Protection circuit module and battery pack incorporating the same

ABSTRACT

The protective circuit module includes a substrate, electronic components mounted on the substrate for constituting a protective circuit, a molding formed on the substrate to enclose the electronic components, and terminal plates connected to appropriate portions of the substrate for connecting the protective circuit to a rechargeable battery. The molding includes a cover surface oriented opposite to the substrate and projections integrally formed on the cover surface to project therefrom.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a protection circuit module for arechargeable battery and to a battery provided with such a protectivecircuit module.

2. Description of the Related Art

A battery pack for use as a rechargeable power source of portableterminal equipment such as a cellular phone is provided with aprotective circuit for preventing a rechargeable battery fromovercharging or overdischarging. For convenience in assembling thebattery pack, such a protective circuit is generally provided as amodule.

FIG. 8 schematically illustrates an example of battery pack 30comprising such a conventional protective circuit module 10 and arechargeable battery 40 which are housed in a case 20.

The protective circuit module 10 basically comprises an insulatingsubstrate 11 which is formed of e.g. glass-fiber-reinforced epoxy resinand has a surface on which electronic components for constituting aprotective circuit are mounted and sealed by a molding 13, and conductorplates 14, 15 each having an end connected to the substrate 11 forconnecting the protective circuit to the rechargeable battery 40. Eachof the conductor plates 14 and 15 has another end connected to apositive electrode 41 or a negative electrode 42 provided on an outershell of the rechargeable battery 40 by spot welding, for example. Inthe example shown in FIG. 8, a plurality of terminals 16 are formed on asurface of the substrate 11 opposite to the surface formed with themolding 13. With the protective circuit module 10 housed in the case 20,the terminals 16 are exposed to the outside through a window 21 formedin the case 20 for electrically connecting the battery pack 30 to thebody of the portable terminal equipment. Through the terminals 16,charging current from a charger is supplied via the portable equipmentbody to the battery pack 30 and discharging current from the batterypack 30 is supplied to the portable equipment body.

The rechargeable battery 40 generally has a rectangular configurationhaving a predetermined thickness. Generally, the positive electrode 41(or the negative electrode, which holds true hereinafter) is provided asa projection formed centrally on one of longitudinally opposite endsurfaces of the battery, whereas the negative electrode 42 (or thepositive electrode, which holds true hereinafter) comprises the entireconductor surface of the battery except the positive electrode. As shownin FIG. 8, to connect the conductor plate 14 to the positive electrode41 in the form of a projection, the conductor plate need be bent at aright angle relative to the substrate 11 and again bent at a right angleto provide a portion 14 b extending parallel to the end surface of thebattery, and the portion 14 b need be connected to the positiveelectrode 41 by spot welding.

As described above, since the entire outer shell of the rechargeablebattery 40 except the positive electrode 41 constitutes the negativeelectrode, the horizontal portion 14B of the conductor plate 14 need beprevented from inadvertently coming into short-circuit contact with theouter shell of the battery. Generally, to cope with the need, anon-illustrated spacer is interposed between the protective circuitmodule 10 and the end surface 40 a of the rechargeable battery 40.

However, such a coping method increases the number of parts of thebattery pack 30 and deteriorates the efficiency in assembling the pack,which results in an increase in the manufacturing cost of the batterypack.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a simplestructure which can be provided without increasing the cost and which iscapable of preventing a conductor plate of the module for connection toa battery from inadvertently coming into shorting contact with theopposite electrode of the battery surface in assembling the batterypack.

According to a first aspect of the present invention, there is provideda protective circuit module comprising a substrate, an electroniccomponent mounted on the substrate for constituting a protectivecircuit, a molding formed on the substrate to enclose the electroniccomponent, and terminal plates connected to appropriate portions of thesubstrate for connecting the protective circuit to a rechargeablebattery. The molding includes a cover surface oriented opposite to thesubstrate and a projection integrally formed on the cover surface toproject therefrom.

Preferably, the projection comprises a resin solidified in a resininjection port of a mold used for forming the molding.

Preferably, the cover surface is integrally formed with a plurality ofprojections.

Preferably, one of the terminal plates includes a through-hole forinserting the projection.

According to a second aspect of the present invention, there is provideda battery pack comprising a case, at least one rechargeable batteryhoused in the case, and a protective circuit module housed in the case.The protective circuit module comprises a substrate, an electroniccomponent mounted on the substrate for constituting a protectivecircuit, a molding formed on the substrate to enclose the electroniccomponent, and terminal plates connected to appropriate portions of thesubstrate for connecting the protective circuit to the rechargeablebattery, and the molding includes a cover surface oriented opposite tothe substrate and a projection integrally formed on the cover surface toproject therefrom. The protective circuit module is arranged in the casewith the projection pressed against the rechargeable battery so that theprojection defines a distance between the rechargeable battery and theprotective circuit module.

According to a third aspect of the present invention, there is provideda battery pack comprising a case, at least one rechargeable batteryhoused in the case, and a protective circuit module housed in the case.The protective circuit module comprises a substrate, an electroniccomponent mounted on the substrate for constituting a protectivecircuit, a molding formed on the substrate to enclose the electroniccomponent, and terminal plates connected to appropriate portions of thesubstrate for connecting the protective circuit to the rechargeablebattery, and the molding includes a cover surface oriented opposite tothe substrate and a projection integrally formed on the cover surface toproject therefrom. The protective circuit module is positioned bybringing the projection of the molding into engagement with anengagement portion formed at an inner surface of the case.

According to the second and the third aspects of the present invention,the projection integrally formed on the molding functions as a spacer inthe battery pack or functions as positioning means. With such astructure, it is possible to properly define the positional relationshipbetween the rechargeable battery and the protective circuit module orthe positional relationship between the protective circuit module andthe case.

Other objects, features and advantages of the present invention willbecome clearer from the description of the preferred embodiment givenbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view illustrating a battery pack according toan embodiment of the present invention.

FIG. 2 is a perspective view illustrating the connection relationshipbetween a protective circuit module and a rechargeable battery in thebattery pack shown in FIG. 1.

FIG. 3 is a partial perspective view illustrating a protective circuitmodule for use in the battery pack shown in FIG. 1.

FIG. 4A illustrates the state wherein a substrate on which necessaryelectronic components are mounted is sandwiched between upper and lowermold members in a process step for forming a molding of a protectivecircuit module.

FIG. 4B illustrates the state in which the upper mold member is removedafter injecting and solidifying a resin in a process step for formingthe molding of the protective circuit module.

FIG. 5 is a schematic plan view illustrating a battery pack according toanother embodiment of the present invention.

FIG. 6 is a sectional view taken along lines VI—VI in FIG. 5.

FIG. 7 is a sectional view taken along lines VII—VII in FIG. 5.

FIG. 8 illustrates a prior art structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowin detail with reference to FIGS. 1–7 . In these figures, parts orportions which are identical or similar to those of the prior artstructure shown in FIG. 8 are designated by the same reference signs.

FIG. 1 schematically illustrates a battery pack 30 embodying the presentinvention, which comprises a casing 20 accommodating a protectivecircuit module 10 together with a rechargeable battery 40.

The protective circuit module 10 has a basic structure whereinelectronic components 12 for constituting a protective circuit aremounted on one surface of an insulating substrate 11 formed of e.g.glass-fiber-reinforced epoxy resin as sealed in a molding 13, whileconductor plates 14 and 15 each has an end connected to the substrate 11for connecting the protective circuit to the rechargeable battery 40.Specifically, the substrate 11 comprises a short plate strip having a,width corresponding to the thickness of the rechargeable battery 40 andhaving one surface provided with necessary electronic components 12 (SeeFIGS. 4A, 4B) as enclosed by the molding 13. The other surface of thesubstrate is formed with a plurality of terminals 16 and has oppositeends to which respective base ends of the conductor plates 14 and 15 areconnected by soldering for example. Each of the conductor plates is ashort strip extending longitudinally out from the substrate 11. Theconductor plates 14 and 15 are formed of a nickel-based material in viewof the suitability for soldering to the substrate 11 and for spotwelding to the aluminum surface of the rechargeable battery 40.

The protective circuit module 10 having the above-described structure isbuilt in the case 20 together with the rechargeable battery 40 as shownin FIG. 1, for example, thereby providing the battery pack 30.Specifically, the protective circuit module 10 is so arranged that onesurface thereof, i.e. the surface provided with the molding 13 faces oneend surface 40 a of the rechargeable battery 40. The conductor plates 14and 15 bent in a predetermined manner are respectively connected to apositive and a negative electrodes 41 and 42 provided at outer surfacesof the rechargeable battery 40 by spot welding. The terminals 16provided on the other surface of the substrate 11 are exposed to theoutside through a window 21 formed at an end surface of the case 20 forelectric contact with the terminals of a portable equipment, therebyperforming reception of a charging current via the main unit of theportable equipment and discharging to the main unit of the portableequipment.

In the present invention, the molding 13 of the protective circuitmodule 10 is integrally formed with projections 17. Specifically, themolding 13 has a thickness depending on the height of the electroniccomponents 12 to be enclosed therein and has a substantially flat coversurface 13 a on the side opposite to the substrate 11. Each of theprojections 17 is integrally formed on the cover surface 13 a to have apredetermined height. In the illustrated embodiment, two columnarprojections 17 are provided as spaced longitudinally of the molding 13.However, the projection 17 may have any other shape such as a prism, aplate or an angled shape. The number and layout of the projections arenot limitative.

The height of each projection 17 is so set that an end of the projection17 abuts the end surface 40 a of the rechargeable battery 40 forpreventing the rechargeable battery 40 and the protective circuit module10 from deviating in the case 20. In this way, the projection 17 servesas a spacer between the rechargeable battery 40 and the protectivecircuit module 10. As mentioned in the description of the related art,one of the positive and the negative electrodes 41 and 42 of therechargeable battery 40 comprises a projection formed at a centerportion of the end surface 40 a of the rechargeable battery 40, whereasthe other electrode is provided by the entire Outer shell of therechargeable battery 40. Therefore, in extending the conductor plate 14to the positive electrode or negative electrode in the form of aprojection, it is necessary to prevent the conductor plate 14 frominadvertently coming into contact with the outer shell of therechargeable battery. However, in the illustrated embodiment, anadditional spacer for such a purpose need not be provided. As shown inFIG. 2, depending on the position of the projection 17, a through-hole18 for passing the projection 17 may be formed in the conductor plate14, as required.

The projection 17 can be easily formed in forming the molding 13 on thesubstrate 11 with the use of mold members 51 and 52 by utilizing gates54 for injecting a resin into a cavity 53 of the mold member 51.Specifically, as shown in FIG. 4A, the substrate 11 on which necessaryelectronic components 12 are mounted is sandwiched between the upper andlower mold members 51 and 52, and a resin is injected into the cavity 53through one end of each gate 54 using an injection nozzle 60. The resinmay preferably be a thermoplastic resin such as polyamide for injectionin a molten state. As shown in FIG. 4B, when the upper mold member 51 isremoved after the solidification of the injected resin, projections 17each having a configuration corresponding to the gate 54 remains on themolding 13 as projecting from the cover surface 13 a. Then, theprojections 17 are cut at a predetermined height position h from thecover surface 13 a of the molding 13. In this way, the projections 17are formed without increasing the number of process steps or without theneed for changing the mold members.

FIGS. 5–7 illustrate battery pack 30 utilizing a protective circuitmodule 10 according to a second embodiment. In this embodiment, theprotective circuit module 10 includes a substrate 11 which is arrangedperpendicularly to an end surface 40 a of a rechargeable battery 40 sothat a cover surface 13 a of a molding 13, which is formed withprojections 17, faces an inner surface of a case 20. Accordingly, theconductor plates 14 and 15 are so connected as to extend widthwise ofthe substrate 11 and bent in the same direction as the projectingdirection of the projections 17 to provide bent portions which areconnected to auxiliary conductor plates 14A and 15A, respectively. Eachof the auxiliary conductor plates 14A and 15A is connected to a positiveelectrode 41 or a negative electrode 42 by spot welding, for example.Terminals 16 formed on a surface of the substrate 11 are exposed to theoutside through a window 21 formed in a lid 22 of the battery pack 30for electric contact with the terminals of a portable equipment, therebyperforming reception of a charging current via the main unit of theportable equipment and discharging to the main unit of the portableequipment.

The inner surface of the case 20 facing the molding 13 is integrallyformed with a boss hole 23 for fitting each projection 17. Such astructure makes it possible to properly position the protective circuitmodule 10 thicknesswise, lengthwise and widthwise of the battery pack atthe same time. In this embodiment, the boss hole 23 for fitting theprojection 17 is formed in the case 20. However, an engagement portionformed at the case my have any other configuration if only it can engagethe projection 17.

Of course, the scope of the present invention is not limited to theabove-described embodiments, and any modification within the scope ofthe following claims is included in the scope of the present invention.Further, the configuration of the substrate for constituting theprotective circuit module, the position and number of the terminals, orthe existence or nonexistence of a terminal block provided instead ofthe terminals does not affect the defining of the scope of the presentinvention.

1. A protective circuit module comprising a substrate having a firstsurface and a second surface opposite to the first surface, anelectronic component mounted on the second surface of the substrate forconstituting a protective circuit, a molding formed on the secondsurface of the substrate to enclose the electronic component, andterminal plates connected to the first surface of the substrate forconnecting the protective circuit to a rechargeable battery; wherein themolding includes a cover surface oriented opposite to the first surfaceof the substrate and a projection integrally formed on the cover surfaceto project therefrom; and wherein one of the terminal plates is bent tointersect the projection, said one terminal plate being formed with athrough-hole in which the projection is inserted to project beyond saidone terminal plate.
 2. The protective circuit module according to claim1, wherein the projection comprises a resin solidified in a resininjection port of a mold used for forming the molding.
 3. The protectivecircuit module according to claim 1, wherein the cover surface isintegrally formed with a plurality of projections.
 4. A battery packcomprising a case, at least one rechargeable battery housed in the case,and a protective circuit module housed in the case, wherein theprotective circuit module comprises a substrate having a first surfaceand a second surface opposite to the first surface, an electroniccomponent mounted on the second surface of the substrate forconstituting a protective circuit, a molding formed on the secondsurface of the substrate to enclose the electronic component, andterminal plates connected to the first surface of the substrate forconnecting the protective circuit to the rechargeable battery, themolding including a cover surface oriented opposite to the first surfaceof the substrate and a projection integrally formed on the cover surfaceto project therefrom, one of the terminal plates being bent to intersectthe projection, said one terminal plate being formed with a through-holein which the projection is inserted to project beyond said one terminalplate, the protective circuit module being arranged in the case with theprojection pressed against the rechargeable battery beyond thethrough-hole of said one terminal plate so that the projection providesa spacing between the rechargeable battery and the protective circuitmodule.